Giuseppe Coppola

Bio: Giuseppe Coppola is an academic researcher from National Research Council. The author has contributed to research in topics: Digital holography & Holography. The author has an hindex of 40, co-authored 256 publications receiving 5489 citations. Previous affiliations of Giuseppe Coppola include Seconda Università degli Studi di Napoli & University of Naples Federico II.

Critically coupled silicon Fabry-Perot photodetectors based on the internal photoemission effect at 1550 nm

Abstract: In this paper, design, fabrication and characterization of an all-silicon photodetector (PD) at 1550 nm, have been reported. Our device is a surface-illuminated PD constituted by a Fabry-Perot microcavity incorporating a Cu/p-Si Schottky diode. Its absorption mechanism, based on the internal photoemission effect (IPE), has been enhanced by critical coupling condition. Our experimental findings prove a peak responsivity of 0.063 mA/W, which is the highest value obtained in a surface-illuminated IPE-based Si PD around 1550 nm. Finally, device capacitance measurements have been carried out demonstrating a capacitance < 5 pF which has the potential for GHz operation subject to a reduction of the series resistance of the ohmic contact.

Analysis of feasibility on the use of fiber Bragg grating sensors as ultrasound detectors

Abstract: The spectral response changing of a Fiber Bragg grating due to the interactions with an ultrasound wave have been numerically analyzed by a transfer matrix approach has been used, taking into account the geometrical and elasto-optic effects. Numerical analysis show that it's possible to characterize the ultrasound wave, only if the ratio between the ultrasonic wavelength and the length of the used grating exceeds an established value, which depends on both the characteristics of the Bragg grating and the ultrasound amplitude itself.

Sexing river buffalo (Bubalus bubalis L.), sheep (Ovis aries L.), goat (Capra hircus L.), and cattle spermatozoa by double color FISH using bovine (Bos taurus L.) X- and Y-painting probes

Abstract: River buffalo, sheep, and goat spermatozoa were cross-hybridized using double color fluorescence in situ hybridization (FISH) with bovine Xcen- and Y-chromosome painting probes, prepared by DOP-PCR of laser-microdissected-catapulted chromosomes, to investigate the possibility of using bovine probes for sexing sperm of other members of the family Bovidae. Before sperm analysis, the probes were hybridized on metaphase chromosomes of each species, as control. Frozen-thawed spermatozoa of cattle, river buffalo, sheep, and goat were decondensed in suspension with 5 mM DTT. Sperm samples obtained from three individuals of each species were investigated, more than 1,000 spermatozoa were scored in each animal. FISH analysis of more than 12,000 sperm revealed high level of sperm with X- or Y-signals in all of the species investigated, indicating FISH efficiency over 99%. Significant interspecific differences were detected in the frequency of aberrant spermatozoa (aneuploid and diploid) between goat (0.393%) and sheep (0.033%) (P < 0.01), goat and cattle (0.096%) (P < 0.5), as well as between river buffalo (0.224%) and sheep (P < 0.5). There was no significant difference between river buffalo and cattle. The present study demonstrated that it is possible to use bovine X-Y painting probes for sexing and analyzing sperm of other species of the family, thus facilitating future studies on the incidence of chromosome abnormalities in sperm as well as on sex predetermination of embryos for the livestock industry. Mol. Reprod. Dev. 67: 108–115, 2004. © 2004 Wiley-Liss, Inc.

How do spermatozoa activate oocytes

Abstract: Although the spermatozoon is 500,000 times smaller in volume than the oocyte, it induces rapid and dramatic changes in oocyte physiology that lead to meiosis re-initiation. These oocyte activation events are described here, as is the evidence for a soluble activating factor in the spermatozoon. Since changes in plasma membrane conductance, calcium ion release and maturation-promoting factor inactivation are common to all animal oocytes at activation, it is expected that the sperm-borne trigger is also ubiquitous. One likely candidate, phospholipase C (PLC) zeta 1, induces calcium release in mammalian oocytes; however, work on other deuterostomes suggests that the sperm factor is non-specific and multifactorial, regulating several activation events. Human, sea urchin and ascidian gametes are remarkably similar and comparative studies across the deuterostomes may help in elucidating basic principles in fertilization. Questions to be answered include the identification of PLC zeta 1 in invertebrate spermatozoa and the characterization of other targets in mammalian oocytes, such as the adenosine diphosphate ribose/nitric oxide pathway.

Excitation of Bloch Surface Waves on an Optical Fiber Tip

Abstract: DOI: 10.1002/adom.201800477 to the development of extremely sensitive surface plasmon resonance (SPR) biosensors, which can rely on mature fabrication technologies, standard biofunctionalization protocols, and commercial scale production.[1,3–5] In spite of the excellent performance achieved by state-of-the-art SPR platforms, with reported limits of detection (LODs) approaching 10−7 refractive index units (RIU),[4,6] further improvements are unavoidably limited by the reliance on lossy materials (typically metals). This yields an undesirable resonance broadening, thereby posing an upper bound to the overall figure of merit (FOM).[6] For this reason, there is a strong push to explore alternative, larger-FOM SW implementations.[1,7–11] As a prominent example, Bloch SWs (BSWs) on truncated 1D photonic crystals (1DPCs) represent an attractive alternative to SPPs, as recently demonstrated in several proof-of-principle studies.[9,12–16] In spite of sensitivities to local refractive index (RI) changes lower than SPR platforms, the completely dielectric low-loss structure of a BSW sensor yields sensibly sharper resonances, leading to generally larger FOMs.[13–17] This has recently led to the successful development of label-free biosensors exhibiting competitive performance in practical biomolecular detections.[18–25] Moreover, BSW structures offer further benefits with respect to other SW-based counterparts, such as easy realization and experimental observation, and great flexibility in terms of wavelength range of operation, materials choice, and tailoring of the field distribution for specific sensing applications.[1,9,13–15,17,26–28] While most sensing platforms proposed in the literature rely on bulky prism-coupled planar configurations,[12–26] the integration of BSW structures with optical fibers would bring significant benefits in terms of compactness, light weight, remote sensing capability, biocompatibility, and ease of interrogation. This is especially attractive within the emerging “labon-fiber” technology framework.[29–34] The interest in this topic has started growing within the last two years, as witnessed by theoretical studies of BSW sensors based on the use of D-type fibers,[35] and unclad regions of multimode fibers.[36] A first experimental demonstration on a tapered single-mode fiber has also been provided very recently.[37] Within this context, a more intriguing scenario is represented by the integration of the resonant structure directly on the fiber tip. This would allow exploiting fabrication methodologies typically adopted for photonic biochips, thereby enabling the development of probes The integration of structures supporting Bloch surface waves (BSWs) with optical fibers is highly desirable, since it would enable the development of high-figure-of-merit miniaturized all-fiber optrodes, opening new pathways within the “lab-on-fiber” roadmap. Here, the first experimental demonstration of grating-assisted excitation of BSWs on the tip of single-mode fibers in the near-infrared region is provided. This is attained via fabrication of a 1D diffraction grating on the fiber facet, and subsequent deposition of a 1D photonic crystal. In spite of a resonance broadening due to grating-induced morphological perturbations, the measured Q-factor of 50 is still higher than typical lab-on-tip plasmonic-probe benchmarks. With a view toward biomolecular sensing, a surface sensitivity of 1.22 nm nm−1 of homogeneous overlay deposited over the active region, which is in line with most plasmonic optrodes largely used in connection with optical fibers, is evaluated. The results also highlight the current limitations and the challenges to face for the development of advanced BSW-based fiber-tip platforms for biological sensing applications. Optical Fiber Sensors

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Photonic crystals

Abstract: The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

Micrometre-scale silicon electro-optic modulator

Abstract: Metal interconnections are expected to become the limiting factor for the performance of electronic systems as transistors continue to shrink in size. Replacing them by optical interconnections, at different levels ranging from rack-to-rack down to chip-to-chip and intra-chip interconnections, could provide the low power dissipation, low latencies and high bandwidths that are needed. The implementation of optical interconnections relies on the development of micro-optical devices that are integrated with the microelectronics on chips. Recent demonstrations of silicon low-loss waveguides, light emitters, amplifiers and lasers approach this goal, but a small silicon electro-optic modulator with a size small enough for chip-scale integration has not yet been demonstrated. Here we experimentally demonstrate a high-speed electro-optical modulator in compact silicon structures. The modulator is based on a resonant light-confining structure that enhances the sensitivity of light to small changes in refractive index of the silicon and also enables high-speed operation. The modulator is 12 micrometres in diameter, three orders of magnitude smaller than previously demonstrated. Electro-optic modulators are one of the most critical components in optoelectronic integration, and decreasing their size may enable novel chip architectures.

Silicon optical modulators

Abstract: Optical technology is poised to revolutionize short-reach interconnects. The leading candidate technology is silicon photonics, and the workhorse of such an interconnect is the optical modulator. Modulators have been improved dramatically in recent years, with a notable increase in bandwidth from the megahertz to the multigigahertz regime in just over half a decade. However, the demands of optical interconnects are significant, and many questions remain unanswered as to whether silicon can meet the required performance metrics. Minimizing metrics such as the device footprint and energy requirement per bit, while also maximizing bandwidth and modulation depth, is non-trivial. All of this must be achieved within an acceptable thermal tolerance and optical spectral width using CMOS-compatible fabrication processes. This Review discusses the techniques that have been (and will continue to be) used to implement silicon optical modulators, as well as providing an outlook for these devices and the candidate solutions of the future.

A high-speed silicon optical modulator based on a metal–oxide–semiconductor capacitor

Abstract: Silicon has long been the optimal material for electronics, but it is only relatively recently that it has been considered as a material option for photonics1. One of the key limitations for using silicon as a photonic material has been the relatively low speed of silicon optical modulators compared to those fabricated from III–V semiconductor compounds2,3,4,5,6 and/or electro-optic materials such as lithium niobate7,8,9. To date, the fastest silicon-waveguide-based optical modulator that has been demonstrated experimentally has a modulation frequency of only ∼20 MHz (refs 10, 11), although it has been predicted theoretically that a ∼1-GHz modulation frequency might be achievable in some device structures12,13. Here we describe an approach based on a metal–oxide–semiconductor (MOS) capacitor structure embedded in a silicon waveguide that can produce high-speed optical phase modulation: we demonstrate an all-silicon optical modulator with a modulation bandwidth exceeding 1 GHz. As this technology is compatible with conventional complementary MOS (CMOS) processing, monolithic integration of the silicon modulator with advanced electronics on a single silicon substrate becomes possible.